PGA309EVM-USB: PGA309EVM-USB

Hi Joseph,

I see you are referring to this post: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/981746/pga309evm-usb-after-calibration-is-complete-eeprom-calibration-data-are-all-zeros in which Luis supported you.

In the old post you were using the 4-wire output mode but it appears that you have switched to three-wire. Can you confirm that you are now using the three-wire configuration on your custom PGA309 board? I will use your Pre-Cal file and attempt to replicate the issue on the PGA309EVM in the three-wire output mode.

Regards,

Zach

Zach,

Thanks for the response! Yes I have been using 3wire mode successfully on both the Multi-Cal system and the PGA309EVM-USB. Currently I am directly connected to the USB-DAQ Platform with my custom PCB.

Is Luis still around or has he moved on? He was a nice guy. Send him my regards and again thanks for looking into this.

Best Regards,

Joe

Hi Joseph,

Nice to hear from you; glad you have been successful with the PGA309 application.  Thank you for your continued interest on the PGA309. Zach and I are part of the same team.  Zach will be working to reproduce the issue on the bench, and get back to you as soon as possible.

 Thank you very much,

Kind Regards,

Luis

Hi Joe,

Thank you for your patience while I've been looking into this. I was able to replicate the error with incomplete EEPROM values using your pre-cal settings and the PGA309EVM-USB.

I believe the issue is related to the "ADC Pre Gain" setting in the "Config Temp" section of the pre-cal file. From my tests, setting the ADC Pre Gain to 1V/V allows the EEPROM values to be filled correctly. Try making this change in your pre-cal file, or for convenience I attached the pre-cal file I used for my test. The only difference between these files is register 6 which contains the ADC Pre Gain setting.

Please let me know if this fix works in your system.

[PGA309_Settings]
Numb Reg=3
Poly Order=2
Output Mode=1
Vout_High_Target=4.500000
Iout_High_Target=0.000000
Iout_Low_Target=0.000000
Vout_Low_Target=0.500000
Vs=5.000000
Vref=4.096000
Calibrate Nonlin=TRUE
Reg0=0
Reg1=0
Reg2=0
Reg3=3328
Reg4=0
Reg5=0
Reg6=5203
Reg7=0
Reg8=0
Temp0=54.444000
Temp1=23.888000
Temp2=-1.111000

Thanks,

Zach

I tried unsuccesfully to upload the image, sorry. note also that I have moved to Windows 11. Do you think this could be the problem?

finally got it to you

Hi Joseph,

Can you provide a photo of your test set-up including the connections to the USB-DAQ? A wiring diagram would be helpful as well.

Do you have a PGA309EVM on hand? Can you connect the PGA309EVM in 3-wire mode to the USB-DAQ and attempt calibration using the sensor emulator? I notice the "auto-continue" feature on the "auto-cal" tab can cause timing issues in the 3-wire configuration so you will need to click the "continue" button manually after each step just as you would with an external sensor.

The PGA309 software is compatible with windows 11 and I was able to successfully calibrate on both windows 10 and 11 using the pre-cal file I sent previously. Can you provide a screenshot of your "set up cal" tab like the one below? Can you also send your updated pre-cal file that you have been using?

One more thing for now... go to the "EEPROM" page and select the "load EEPROM with file" button then select the EEPROM file I've attached here. Then use the "read EEPROM" button to verify that the EEPROM is being written and read from correctly. After loading and reading this file your EEPROM tab should look like the image below. Then you compare to the results after attempting your calibration.

[General Info]
Date=1/27/2023
Time="2:25 PM"
[Paths]
Model path="/c/program files (x86)/proj_pga309evm-usb/Model_Files/JAN27_custTest1.txt"
Pre-Cal path="/c/program files (x86)/proj_pga309evm-usb/Pre_Cal_Files/PreGain1V.txt"
Sensor Emulator path="/c/program files (x86)/proj_pga309evm-usb/Sensor_Emulator_Files/nonlin.csv"
[EEPROM Data]
Addr0=21577
Addr2=0
Addr4=0
Addr6=3344
Addr8=10005
Addr10=0
Addr12=5203
Addr14=25406
Addr16=21472
Addr18=36153
Addr20=24940
Addr22=21582
Addr24=65388
Addr26=266
Addr28=21688
Addr30=65404
Addr32=228
Addr34=21792
Addr36=65421
Addr38=183
Addr40=21892
Addr42=65442
Addr44=141
Addr46=21989
Addr48=65463
Addr50=93
Addr52=22083
Addr54=65485
Addr56=41
Addr58=22174
Addr60=65506
Addr62=65522
Addr64=22262
Addr66=65534
Addr68=65464
Addr70=22346
Addr72=22
Addr74=65399
Addr76=22428
Addr78=50
Addr80=65334
Addr82=22506
Addr84=86
Addr86=65258
Addr88=22581
Addr90=117
Addr92=65182
Addr94=22653
Addr96=153
Addr98=65099
Addr100=22721
Addr102=196
Addr104=65002
Addr106=22787
Addr108=237
Addr110=64908
Addr112=22849
Addr114=290
Addr116=64797
Addr118=32767
Addr120=0
Addr122=54559

Thanks,

Zach

Zach,

Sorry it has taken me so long to respond. I do very much appreciate your support! 

I followed through with installing the PGA309 EVM in 3 wire mode. It worked properly and calibrated. I realized right away when I hooked it up that I did not wire my device correctly. In this application we are taking advantage of the temperature coeficient of the attached bridge using a fixed resistor on the high side to get the temperature. I am using the Burr Brown sensor emmulator. I made the following mistakes.

1) I did not connect the temperature wire.

2) I did not properly modify the circuit board to use the signal from the Burr Brown sensor emmulator. (The sensor emmulator DOES NOT act the same as a resistive bridge! All the signals are buffered with opamps. When connecting my board I must remove the series pass resistor that is used for temperature measurement from the exc pin or the PGA does not calibrate right.)

I also found another problem. I have 2 USB DAQ Platforms. One is working perfectly calibrating from .5 to 4.5v very well. Unfortunately I was using the one that does not work correctly. It does calibrate but the AtoD converter is not quite right it thinks that 4.585v is 4.5 v and .51 is .5. The computer shows 4.5 v and .5 v respectively on the screen when it calibrates but using 2 different independant meters the output is actually 4.585 and .51v. 

All these issues made a perfect storm of problems. It is now resolved at least with the correctly working USB DAQ Platform. 

I have looked at the datasheet for the Ato D converter used on the USB DAQ Platform and may try to replace it to resolve the problem. I have confirmed that the reference used in circuit is working correctly and there really isn much else to test. If you have any suggestions let me know.

Thanks again for the support!

Best,

Joe

Hi Joe,

That is great! Thanks for letting us know how you were able to resolve this issue, it is very helpful when we look back at these threads in the future.

Just to clarify, you have one working USB-DAQ that you are able to successfully calibrate and write to EEPROM on your device?

Regards,

Zach

Zach,

Both USB- DAQ's calibrate the PGA309 fine. It is just that one of them has an AtoD error. THe AtoD reports 4.5v when the actual voltage at the PGA309 output is 4.585v and .5v when it is actually .51v. The computer is displaying 4.5 and .5 respectively during the calibration at every calibration point. The computer can only use the information the AtoD gives it to calibrate and that is what it is doing.

Just as an experiment I reduced the set points for calibration by .085v and .01 and got a nice calibration of the PGA309 to output 4.5 and .5. The computer thinks it is calibrating to 4.415v (4.5-.085v) and .49v (.5-.01) and displays the calibration points as such but again the actual output is 4.5 and .5.

I was considering just replacing the AtoD it is only a 6 pin sot-23 packaged part. Note that I verified the reference voltage for the AtoD is correct and the AtoD is internaly self calibrating with no other mechanism to adjust it.

Best,

Joe